This invention relates in general to devices for MicroElectroMechanical Systems (MEMS), and in particular to a microvalve device in the form of a microvalve formed of a valve component defining a cavity, the valve component being movable within a microvalve body, the microvalve body defining a non-linear flow path that communicates with the cavity defined in the valve component.
MEMS (MicroElectroMechanical Systems) is a class of systems that are physically small, having features with sizes in the micrometer (micron) range. These systems have both electrical and mechanical components. The term “micromachining” is commonly understood to mean the production of three-dimensional structures and moving parts of MEMS devices. MEMS originally used modified integrated circuit (computer chip) fabrication techniques (such as chemical etching) and materials (such as silicon semiconductor material) to micromachine these very small mechanical devices. Today there are many more micromachining techniques and materials available. The term “micromachined device” as used in this application means a device having features with sizes in the micrometer range, and thus by definition is at least partially formed by micromachining. More particularly, the term “microvalve” as used in this application means a valve having features with sizes in the micrometer range, and thus by definition is at least partially formed by micromachining. The term “microvalve device” as used in this application means a micromachined device that includes a microvalve, and that may include other components. It should be noted that if components other than a microvalve are included in the microvalve device, these other components may be micromachined components or standard sized (larger) components. Similarly, a micromachined device may include both micromachined components and standard sized (larger) components.
Various microvalve devices have been proposed for controlling fluid flow within a fluid circuit. A typical microvalve device includes a displaceable member or valve component movably supported by a body for movement between a closed position and a fully open position. When placed in the closed position, the valve component substantially blocks or closes a first fluid port that is otherwise in fluid communication with a second fluid port, thereby preventing fluid from flowing between the fluid ports. When the valve component moves from the closed position to the fully open position, fluid is increasingly allowed to flow between the fluid ports.
U.S. Pat. No. 6,505,811, the disclosures of which are incorporated herein by reference, describes a microvalve device that consists of two microvalves, one microvalve acting as a pilot valve, and a second microvalve acting as a pilot-operated valve. Each of these microvalves is made of multiple layers of material which are micromachined and bonded together to form a microvalve body, and the various microvalve components contained therein.
In the microvalve acting as a pilot valve, the valve component is a pivoting component, and consists of a beam resiliently supported by the body at one end. In operation, an actuator forces the beam to bend about the supported end of the beam, moving from an unactuated position toward an actuated position. The beam is formed from an intermediate layer of material and pivots within a chamber defined by the intermediate layer and by the layers immediately adjacent to the intermediate layer. When the actuator is deenergized, the bending forces return the beam back toward the unactuated position. In this manner, a fluid flow path through a port in the body can be selectively blocked by movement of the beam between a position blocking the port and a position not blocking the port.
In the microvalve acting as a pilot operated microvalve, the valve component is a sliding component, and consists of a slider element formed from an intermediate layer of material. The slider element is guided so as to be able to reciprocate within a chamber defined by the intermediate layer and by the layers immediately adjacent to the intermediate layer. In operation, a control pressure in the form of pressurized fluid from the pilot microvalve acts on a first longitudinal end face of the slider element to urge the slider element to slide from an unactuated position toward an actuated position. In this manner, a fluid flow path through a port in the body can be selectively blocked by movement of the slider element between a position blocking the port and a position not blocking the port. In U.S. Pat. No. 6,505,811, the slider element is connected to a fixed portion of the intermediate layer by a spring which returns the slider element to the unactuated position upon a reduction in the fluid pressure exerted by the pilot microvalve. Additionally, fluid pressure can be applied to a second longitudinal end face of the slider element (opposite the first longitudinal end face) to act as a feedback pressure acting in opposition to the control pressure.
Various openings (vents, ducts, or apertures) may be formed perpendicularly (that is, perpendicular to the plane of movement within which the valve components are constrained to move) through the valve component of either a pivoting valve component, generally similar to the beam of the pilot microvalve described above, or through a sliding valve component, generally similar to the slider element of the pilot operated microvalve described above. One effect of such openings help prevent or diminish pressure imbalances between the perpendicularly opposed surfaces of the valve component, so that the valve components are not urged into “out of plane” movement so as to drag against layers of material which are adjacent to the intermediate layer from which the valve components are fabricated.
In the aforementioned U.S. Pat. No. 6,505,811, more than one embodiment of the invention involves a microvalve having a body defining at least two ports, and further defining a cavity within which a slider element is disposed. The slider element defines an aperture therethrough which is sized so that in an open position of the slider element, both ports are in fluid communication with the aperture of the slider element. In the open position, fluid can flow through one of the ports, longitudinally within the aperture of the slider element, and then out of the other port. In a closed position of the slider element though, the aperture of the slider element is no longer in fluid communication with one of the ports; the flow through that port is blocked by a portion of the slider element adjacent to that port.
In U.S. Pat. No. 6,694,998, the disclosures of which are incorporated herein by reference, a microvalve device of my invention is illustrated. The microvalve device is configured as a 3-way microvalve, having a first supply port, an output conduit, and a return port. In a pressure increase position, a slider element allows the fluid to flow from the first supply port to the output conduit. In a pressure hold position, the slider element isolates the output conduit from both the first supply port and the return port. The pressure decrease position allows fluid to flow from the output conduit to the return port. Pressure from the output conduit acts against a first axial end face of the slider element to provide pressure feedback. A single slider valve conduit provides this fluid communication between the output conduit and the first axial end face of the slider element.